1. Field of the Invention
The present invention relates to a variable-capacity exhaust turbocharger equipped with a variable-nozzle mechanism which is used for an exhaust turbocharger of an internal-combustion engine and includes a plurality of nozzle vanes rotatably supported to a nozzle mount, a rotational-driven annular drive ring, and a lever plate of which one end engages with the drive ring and another end is fixed to each nozzle vane, where each blade angle of the plurality of nozzle vanes is changed in such a manner that the lever plate is swung by a rotation of the drive ring.
2. Description of the Related Art
Among comparatively small-size exhaust turbochargers used for a vehicle internal-combustion engine or the like, a double-flow-type variable-capacity exhaust turbocharger equipped with a variable-nozzle mechanism is widely used in which exhaust gas discharged from an engine is filled into a scroll formed in a turbine casing to act on a turbine rotor formed on the inner-peripheral side of each nozzle vane via a plurality of nozzle vanes formed on the inner-peripheral side of the scroll and each blade angle of the plurality of nozzle vanes is capable of being changed.
FIG. 7 is a partially sectional view showing an example of the exhaust turbocharger equipped with the variable-nozzle mechanism according to a conventional art when taken along the rotary axis line. FIG. 8 is a sectional view taken along the line D-D shown in FIG. 7. FIG. 9 is a sectional view taken along the line C-C shown in FIG. 8.
In FIGS. 7 to 9, Reference Numeral 10 denotes a turbine casing and Reference Numeral 11 denotes a scroll having a spiral shape formed in the outer periphery of the turbine casing 10.
Reference Numeral 12 denotes a double-flow-type turbine rotor coaxially formed with a compressor (not shown), and a turbine shaft 12a thereof is rotatably supported to a bearing housing 13 via a bearing 16. Reference Numeral 100a denotes a rotary axis line of the exhaust turbocharger.
Reference Numeral 2 denotes a plurality of nozzle vanes arranged in the inner periphery of the scroll 11 in a circumferential direction at the same interval therebetween, and a nozzle shaft 02 connected to each end portion thereof is rotatably supported to a nozzle mount 4 fixed to the turbine casing 10, thereby changing a blade angle by the use of a variable-nozzle mechanism 100.
In the variable-nozzle mechanism 100, the nozzle vane 2 is disposed between the nozzle mount 4 and an annular nozzle plate 6 coupled to the nozzle mount 4 via a plurality of nozzle support members 5a. The nozzle plate 6 is fitted to an attachment portion of the turbine casing 10.
Reference Numeral 3 denotes a drive ring formed in a disk shape and rotatably supported to the nozzle mount 4, and drive pins 22 are fixed in a circumferential direction at the same interval therebetween.
Reference Numeral 1 denotes a lever plate, where an input-side groove thereof engages with each drive pin 22 and an output side thereof is fixed to the nozzle shaft 02.
Reference Numeral 15 denotes a linkage connected to an actuator (not shown) as a driving source of the nozzle vane 2, and Reference Numeral 10s denotes a crank pin connected to the linkage 15. The crank pin 14 engages with the drive ring 3 so as to rotationally drive the drive ring 3.
Upon operating the variable-capacity exhaust turbocharger equipped with the variable-nozzle mechanism with the above-described configuration, exhaust gas discharged from an engine (not shown) flows into the scroll 11, and flows into the nozzle vane 2 while orbiting along the spiral of the scroll 11. Subsequently, the exhaust gas flows between the blades of the nozzle vane 2 and flows into the turbine rotor 12 from the outer-peripheral side. Subsequently, the exhaust gas flows toward the center in a radial direction to perform an expanding action to the turbine rotor 12 and flows in an axial direction to be guided to a gas outlet 10b, thereby being discharged to the outside.
Upon controlling the capacity of the variable-capacity turbine, in the actuator, a blade angle of the nozzle vane 2 is set by a blade angle control unit (not shown) so that a flow rate of the exhaust gas flowing to the nozzle vane 2 is equal to a required flow rate. A reciprocating displacement of the actuator corresponding to the blade angle is transmitted to the drive ring 3 via the linkage 15 and the crank pin 10s so as to rotationally drive the drive ring 3.
In terms of the rotation of the drive ring 3, the lever plate 1 is rotated in a circumferential direction of the nozzle shaft 02 by the drive pins 22 fixed to the drive ring 3 in a circumferential direction at the same interval therebetween. Subsequently, in terms of the rotation of the nozzle shaft 02, the nozzle vane 2 is rotated, and the blade angle thereof is changed to the blade angle set in the actuator.
Another example of the double-flow-type variable-capacity exhaust turbocharger equipped with the variable-nozzle mechanism is disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-56791).
However, the exhaust turbocharger equipped with the variable-nozzle mechanism according to the conventional art shown in FIGS. 7 to 9 still has the following problems to be solved.
That is, in the variable-nozzle mechanism shown in FIGS. 7 to 9, as shown in FIG. 9, the drive ring 3 is disposed between the lever plate 1 and the nozzle mount 4 in an axial direction, and the drive pin 22 fixed to the drive ring 3 is fitted to the groove is of the lever plate 1 so as to drive the lever plate 1 via the drive ring 3 and the drive pin 22.
For this reason, since the drive pin 22 contacts with the lever plate 1 so as to drive the lever plate 1 via the drive ring 3 and the drive pin 22 on the same plane as the lever plate 1 directly connected to the nozzle vane 2, bending moment occurs at the contact portion between the drive pin 22 and the lever plate 1.
Accordingly, the nozzle shaft 02 supporting the nozzle vane 2 is inclined with respect to a hole formed in the nozzle mount 4, thereby causing local excessive stress. As a result, the nozzle vane 2 cannot be operated regularly, and a portion between the nozzle vane 2 and the lever plate 1 is broken.
FIGS. 10 and 11 show the variable-nozzle mechanism disclosed in Patent Document 1, where FIG. 10 is a front view showing the variable-nozzle mechanism, and FIG. 11 is a sectional view taken along the line E-E shown in FIG. 10.
In this example, the drive pin 22 is fixed to the lever plate 1, and the drive pin 22 is fitted to a groove 3a of the drive ring 3. In this case, since a contact point between the groove 3a of the drive ring 3 and the drive pin 22 is located on the driving-side drive ring 3, the amount of the above-described bending moment is little, thereby hardly causing the above-described problem.
However, in Patent Document 1, it is necessary to reduce a deformation applied from the drive ring 3 to the nozzle shaft 02 by increasing a thickness of the lever plate 1 in consideration of the bending moment at the contact portion between the lever plate 1 and the drive pin 22. For this reason, since the thickness of the lever plate 1 increases, the regular operation of the nozzle vane 2 is disturbed, and a decrease in weight and size in operation is disturbed.